Good start but became nightmarish

Last night I became conscious I'd doped off to sleep but after a promising start it all went rather wrong.

I'd gone off to bed and read a bit of Stephen LaBerge's book on WILD. I had then instructed myself to remember any dreams I had in order to write them down in the morning. I then decide to focus on repeating to my self “when I'm dreaming, I'll recognize I'm dreaming” for a while. I still didn't feel particularly sleepy so I did a little meditation that I'd just read about by imagining there was a lotus flower in my throat with a flame in it's middle. I did get distracted on occasion while doing this but managed to focus on it rather well.

I then dreamed that I was laying in bed and breathing slowly and as I exhaled it was a quiet wail or scream.. I think I did this for about three times at which point I became conscious I had tipped into a sleeping state. Everything was dark so I decided to visualize something. A small hole appeared in the darkness and I could see a corridor in a house with wooden furniture or fittings on the walls.

At this point I became aware I was struggling with my breath, which got worse and I felt I couldn't breath. I dreamed I sat on the edge of my bed struggling for breath and starting to panic. I must have been lucid as I decided to wake myself up and after a short while I heard my partner say “it's alright Rick you're dreaming” and then I was awake.

My partner reported that she had woken me up because my sleep looked quite disturbed. She said I was breathing fine but noisily. I'm really pleased I became lucid as I've been working towards this for a week , but am a little perplexed that it seemed to end in a dream anxiety attack.

Has anyone else experienced anything like this? Any tips, advice or suggestions are very welcome.